1. Field
The inventive concept relates to a distributed antenna system (DAS), and more particularly, to a node unit of a DAS, which enable the DAS to stably provide services.
2. Description of Related Art
In general, a distributed antenna system (DAS) is used to extend the service coverage of a base station in a mobile communication system or solve shadow areas. Recently, studies on a digital DAS for performing digital processing base station signals between node units constituting a DAS and user terminal signals and transmitting the digital-processed signals have been actively conducted due to various reasons such as a decrease in influence of noise, a decrease in transmission capacity, and convenience of signal processing.
In the digital DAS, spurious waves may be generated due to various causes. For example, when the supply of power to a node unit constituting the digital DAS is interrupted due to an unexpected accident, etc., spurious waves may be generated from digital elements (e.g., FPGA, CPU, ADC, DAC, and PLL) in the node unit. Alternatively, when power is supplied to a node unit to which the supply of power is interrupted, the digital elements in the node unit are initialized, and therefore, spurious waves may be generated from the digital elements in the node unit. Alternatively, when the power of a specific node unit or digital elements therein are to be reset as an obstacle occurs in the corresponding node during a normal service, spurious waves may be generated from the digital elements in the node unit.
When spurious waves are generated in a node unit of the DAS, the generated spurious waves may damage a specific signal processing component (e.g., a power amplification unit (PAU)) in the corresponding node unit, or may damage an adjacent node unit communicatively connected to the corresponding node unit as the spurious waves are transmitted to the adjacent node unit. Therefore, the service quality of the DAS is degraded.
Accordingly, there is required a method capable of preventing spurious waves from being generated in a node unit constituting the DAS.